Australia's Great Barrier Reef has just experienced the fourth coral bleaching event in seven years. The rare coral bleaching caused by abnormal sea water temperature is rapidly becoming the norm It is said that this large-scale bleaching affected more than 90% of the coral reefs that make up the system, and it happened for the first time in La Nina.
Coral bleaching occurs under abnormal marine conditions, such as warmer waters. If the symbiotic algae that provide nutrition and colorful appearance leave or die, the coral will turn white and eventually die due to the loss of nutrition supply. Those corals that only experience mild or moderate bleaching have a good chance of recovery, but the rapid and continuous repeated bleaching events have little chance of mitigation.
As we all know, the Great Barrier Reef experienced large-scale bleaching events in 1998, 2002, 2016 and 2017, and then again in 2020. A new report by Australian government scientists shows that it has now experienced the fourth large-scale bleaching event in just seven years.
The water in the whole coral reef system began to warm in early December 2021 and rose to an all-time high usually seen in the local summer. The heat continued until April 2022, including three heat waves in the central and northern regions. As reports of bleaching continued to increase, scientists from the Great Barrier Reef Marine Park Authority conducted an aerial survey of the entire coral reef, which showed the extent of the damage.
The team surveyed 6591 coral reefs and 714 coral reefs to some extent. This is the first large-scale bleaching event of the Great Barrier Reef in La Nina year. The conditions in La Nina year are usually mild.
The scientists also pointed out that the response of corals to thermal stress can be elongated, so although the current situation is very serious, albinism may become more serious in the coming months before the water temperature cools and provides opportunities for recovery.
Scientists wrote in a report entitled reef snapshot: summer 2021-22: "Climate change remains the greatest threat to coral reefs. It affects weather patterns and ocean temperatures, pH and ocean currents, and exacerbates the effects of other threats. Climate change is escalating, and the Great Barrier Reef is already experiencing such consequences. Unfortunately, events that disrupt the Great Barrier Reef are becoming more and more frequent, leaving less time for coral recovery."
The full text of the report is available Online。